People rely on disposable absorbent articles to make their lives easier.
Disposable absorbent articles, such as adult incontinence articles and diapers, are generally manufactured by combining several components. These components typically include a liquid-permeable topsheet; a liquid-impermeable backsheet attached to the topsheet; and an absorbent core located between the topsheet and the backsheet. When the disposable article is worn, the liquid-permeable topsheet is positioned next to the body of the wearer. The topsheet allows passage of bodily fluids into the absorbent core. The liquid-impermeable backsheet helps prevent leakage of fluids held in the absorbent core. The absorbent core generally is designed to have desirable physical properties, e.g. a high absorbent capacity and high absorption rate, so that bodily fluids can be transported from the skin of the wearer into the disposable absorbent article.
Some disposable absorbent articles are constructed with various types of elasticized waistbands and elasticized leg bands or leg cuffs. One method of constructing elasticized regions is to incorporate elastic strands, ribbon, or other material into the disposable absorbent product. For example, elastic strands have been laminated between layers of polymer film and/or layers of woven or nonwoven fabrics to provide such regions. Folded-over layers have also been employed to enclose or envelop selected strands of material. These folded-over layers have been employed to enclose elastomeric strands within the waistband, leg cuff and inner barrier cuff components of disposable diapers and other disposable absorbent articles. The polymeric film or films, layers of woven or nonwoven fabrics, and/or folded-over layers may be an integral portion of the topsheet and/or backsheet discussed above, or may be separate components that are attached to the topsheet and/or backsheet.
In order to introduce an elastic material to the product being made, a spool of the material is generally placed on an unwind stand. For example, a spool of elastic strand on an unwind stand is continuously unwound, in the machine direction, with the strand being attached to a substrate, such as a base layer of material, to provide a substrate composite. As stated above, examples of a base material include, but are not limited to, polymeric films and/or woven or nonwoven fabrics. If a segment of the elastic strand sticks or adheres to a neighboring segment of the elastic strand, then the resulting agglomeration of neighboring segments may be difficult to pull apart when the spool is unwound. In fact, a strand segment may break, leading to costly downtime on a production machine.
What is needed is a method for handling a spool, bobbin, roll, or other container of elastic material so that the material remains substantially unagglomerated; spools, bobbins, rolls, or containers of elastic material in which neighboring segments of the material remain substantially unagglomerated; and substrate composites and absorbent products made using elastic material handled such that the material remains substantially unagglomerated prior to the material""s use as a raw material.
We have determined that neighboring segments of elastic material agglomerate when the material is exposed to water or water vapor. For example, if elastic strand is made at a location different from where the strand is used as a raw material, then the elastic strand must be shipped. During shipping, storage, or other steps the elastic strand may be exposed to amounts of water or water vapor sufficient to cause neighboring segments of the strand to agglomerate. If the strand agglomerates, then it may break more frequently when used as a raw material in a production process (e.g., a conventional, high-speed, disposable-absorbent-article production process running at about 1000 feet per minute or more). Accordingly, the present invention is directed to regulating agglomeration of elastic material by regulating the material""s exposure to water or water vapor.
One method having features of the present invention comprises the steps of providing substantially unagglomerated elastic strand; and regulating exposure of the strand to water or water vapor so that the strand remains substantially unagglomerated.
In one representative embodiment, an elastic strand""s exposure to water or water vapor is regulated such that the specific humidity around the strand does not exceed about 0.017 pounds-mass of water vapor per pound-mass of dry air, specifically about 0.01 pounds-mass of water vapor per pound-mass of dry air, and more specifically about 0.005 pounds-mass of water vapor per pound-mass of dry air during: storage of the strand at the geographic site where the strand is made, shipping of the strand between the geographic site where the strand is made and the geographic site where the strand is to be used as a raw material, storage of the strand at the geographic site where the strand is to be used as a raw material, or some combination thereof. In some versions of the invention, the strand is used as a raw material to produce a substrate composite comprising the strand or an absorbent article comprising the strand.
Another representative embodiment in which an elastic strand""s exposure to water or water vapor is regulated comprises controlling the temperature around the strand or around a container that contains the strand so that the strand remains substantially unagglomerated before the strand""s use as a raw material. In one aspect, the temperature is controlled so that it does not exceed about 55 degrees Fahrenheit. By regulating temperature, the maximum humidity that might be attained is regulated (i.e., as air temperature decreases, the capacity of the air to hold water vapor decreases).
In another embodiment, a method in which an elastic strand""s exposure to water or water vapor is regulated comprises controlling the humidity around the strand or around a container that contains the strand so that the strand remains substantially unagglomerated before the strand""s use as a raw material. In one aspect, the specific humidity is controlled so that it does not exceed about 0.017 pounds-mass of water vapor per pound-mass mass of dry air, specifically about 0.01 pounds-mass of water vapor per pound-mass of dry air, and more specifically about 0.005 pounds-mass of water vapor per pound-mass of dry air.
In some versions of the invention, the elastic strand to which exposure to water or water vapor is regulated comprises polyester, polyurethane, polyether, polyamide, polyacrylate, polyester-b-polyurethane block copolymer, polyether-b-polyurethane block copolymer, or polyether-b-polyamide block copolymer.
Another method having features of the present invention includes the steps of: providing an elastic strand, the elastic strand having been made by steps comprising extruding, spinning, or otherwise making the strand; and regulating the strand""s exposure to water vapor so that the Agglomeration Index Value (defined below) does not exceed about 10 grams per strand, particularly does not exceed about 20 grams per strand, more particularly does not exceed about 25 grams per strand, more specifically does not exceed about 30 grams per strand, and suitably is substantially zero at the time it is used as a raw material on a production machine. In another aspect, the production machine is a machine that incorporates one or more elastic strands into a substrate composite or disposable absorbent article.
In another version of the invention, regulation of an elastic strand""s exposure to water or water vapor comprises the steps of placing the strand in a container comprising a barrier material resistant to penetration by water vapor, and closing the container so that the strand remains substantially unagglomerated.
In another method of the present invention, the container comprising a barrier material is closed at a time t1, time t1being after the time when the strand is first produced and before the time when the strand is shipped from the geographical site where the strand is made to the geographical site where the strand is used as a raw material. In another aspect, the specific humidity around the strand does not exceed about 0.017 pounds-mass of water vapor per pound-mass of dry air, specifically about 0.01 pounds-mass of water vapor per pound-mass of dry air, and more specifically about 0.005 pounds-mass of water vapor per pound-mass of dry air between time t1 and time t2, time t2 being the time at which the closed container comprising a barrier material is first opened.
In yet another aspect, the barrier material comprises polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyester, polycarbonate, nylon, cellulose, or a combination thereof.
In some versions of the invention, the container comprising barrier material is closed by heat sealing the container, barrier material, or both.
Another method having features of the present invention comprises placing desiccant material with the strand before the container comprising a barrier material is closed (e.g., by heat sealing the barrier material). In another aspect, the desiccant material comprises calcium chloride, calcium sulfate, silica gel, a molecular sieve, Al2O3, or some combination of thereof.
Other representative embodiments comprise the steps of displacing any mixture of air and water vapor from the interior of the container comprising a barrier material with an inert dry gas before the container is closed (e.g., by heat sealing the barrier material); placing a humidity indicator inside the container comprising a barrier material before the container is closed (e.g., by heat sealing the barrier material); or both.
Still other representative embodiments of the invention include elastic strand handled such that the strand remains substantially unagglomerated by regulating exposure of the strand to water or water vapor, and substrate composites and disposable absorbent products made using such elastic strand.
These and other versions, features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.